I know that sound like a stupid title, but it's true.
I shall elaborate.
Besides the obvious edible nature of junk food.
Lets take potato chips, as an example.
Potatoes are mostly starch and sugars. That alone is good fuel, but those chips contain a heck of a lot of oil.
In a survival situation, you could quickly light the end of a potato chip and it will burn rather well.
That will save your matches or lighters.
Not only does it burn well, but the excess oil does drip off as it becomes heated and the starches and carbohydrates burn. That oil can be collected and and used for a lot of things. I wouldn't suggest ingesting it at that point though.
Cheese doodles, chips, puffs.
Pretzels burn well too, but not as good. Those are better left for eating.
Crumbled snacks can be used to entice smaller creatures into traps or to within range.

Now, lets turn to the bag.
Most chip bags are silvery on the inside.
Great for signaling.
A chip bag also makes an effective hand warmer.
The silvery inside is just like a space blanket.

The bags themselves are prone to tearing, but they can be used to collect water or other edibles. Other dry goods can be stored in them.
The crinkly nature of the bags, makes for a rather effective tripwire alarm.
To silence the noise on your person, wrap it up in folded clothing.

Again, the silvery bag can be cut into tiny strips and tied to a fish hook for a makeshift, shiner lure.

A folded bit of the bag works as an effective tool to pick your teeth.

In first aid situations, a cleaned out bag can be used to help secure wounds.

Just a few things that I have tried and found rather effective.

Little debbie oatmeal pies offer more calories for your buck than any other ready to eat food.

Snickers has a near perfect ratio of carbs,fat,protien for long term exercise. They are a well known staple for through hikers on the appalachian trail.

Peanut butter and tortillas makes another easy to carry and calorie dense food source.

Junk food will just make you sick and crash...

Yeah you need fat and protein but from hearty and natural meals and more importantly you need NUTRITION

I think what you mean is good hiking food but terrible for survival

Interesting use of bag though.

Yeah, why do you think every trail mix has nuts!
Healthiest foods in the world are nuts, beans, broccoli, insects of all kinds... the ideal trail mix would be that ^_^

One aspect of 'junk food' has been overlooked, the morale factor. A Little Debbie cake can give you a taste of home when you have had a belly-full of caught it, wolfed it down. It is comfort food, and it will give you a morale boost, just the same as being able to bathe/shower/shave.

I thought I replied to this already I guess I didn't. I had some little debbies in my bag, but one by one they disappeared, sorta like my chicken jerky. I need to get serious and restock.